海角大神

With each new advance in personal technology, so much of who we are as individuals becomes more pervasive, extending far beyond a material body. Our daily thoughts or habits can be put into a 鈥渃loud鈥� on the Web. Google or Facebook may contain troves of personal history. Our electronic identities seem more transparent and less earthbound.

Because of these challenges to old notions of personhood, the Supreme Court issued a ruling Wednesday that comes down hard on police conducting arbitrary searches of cellphones used by people arrested for a crime. Such digital devices, from iPads to smart phones, can contain a record of nearly every aspect of a person鈥檚 life 鈥渇rom the mundane to the intimate,鈥� stated Chief Justice John Roberts for the court鈥檚 majority. The proverbial visitor from Mars, he wrote, might conclude that cellphones are 鈥渁n important feature of human anatomy.鈥�

The ruling is not a total embrace of cellphone privacy. Police will still be allowed to search a phone in the case of an extreme emergency, such as an immediate bomb threat or a reasonable risk of evidence being destroyed. But during most arrests, police will need to prove 鈥減robable cause鈥� to a judge and obtain a warrant before fishing for evidence of another crime in a person鈥檚 cellphone.

Protecting privacy is not simply a matter of avoiding arbitrary abuse by government. Yes, the Fourth Amendment ban on 鈥渦nreasonable searches and seizures鈥� was written by the Founding Fathers to prevent the kind of searches conducted by British soldiers in the homes of Colonial Americans. But privacy also helps individuals to thrive. It allows for freedom of thought, solitude for growth, and intimacy of personal relationships. These uses of privacy lie behind the heightened concern to maintain it.

鈥淢odern cellphones aren鈥檛 a technological convenience,鈥� Chief Justice Roberts wrote. 鈥淲ith all they contain and all they may reveal, they hold for many Americans 鈥榯he privacies of life鈥�.鈥�

This ruling reflects the many legal challenges posed by new technologies, such as DNA analysis and GPS tracking. Judges are being asked to sort out the difficult legal distinctions that each new technology brings. In another ruling Wednesday, for example, the Supreme Court decided against Aereo Inc., a service that retransmits signals from broadcast TV to paying customers. The court said the service infringes on copyrighted programming. But as with similar cases, the court hinted it might be better for lawmakers to decide the deeper issues.

In 2012, the high court ruled against police being able to place a GPS tracking device on a suspect鈥檚 car without a warrant. Yet it ruled in 2013 that police could take a DNA sample of anyone under arrest, likening it to fingerprinting. In both rulings, the justices were sharply divided.

Such cases raise moral questions about personal autonomy and the presumption of innocence. The Constitution and previous court decisions can provide limited guidance. It is up to citizens to press lawmakers on how to resolve the issues posed by new technologies. Each person鈥檚 鈥渘ew鈥� identity in the digital universe depends on it.